The official has insisted on anonymity in order to discuss the decision before the official announcement.

"If we lag, the noose tightens", said Princeton University climate scientist Michael Oppenheimer, co-editor of the peer-reviewed journalClimatic Change. And it could trigger further efforts to erode the landmark climate accord.

The mixed messages coming out of the White House left open the possibility that the original news reports reflected the views of officials who were aiming to steer the final outcome by presenting withdrawal as a done deal.

Just how Trump would pull the USA out of the accord remains unclear, Axios notes.

"I will be announcing my decision on the Paris Accord over the next few days".

Trump was to meet later Wednesday with Secretary of State Rex Tillerson, who has favored remaining in the deal.

Over the weekend, some Trump advisers seemed to be favoring this triangulation approach, perhaps combined with a renegotiation of US emissions targets to lower the (arbitrarily set) goals.

After taking office, however, Trump faced pressure to stay in the deal from investors, global powers and business leaders, including some in the coal industry. Citing a senior White House official, ABC said the administration is working on how to roll out the decision. The leaders of the other G7 nations - France, Japan, Canada, the United Kingdom and Italy - all urged Trump to remain a part of the 2015 agreement.

It remains unclear when or how the administration might plan to pull out of the climate agreement, the BBC's Paul Rincon writes. However, his decision to back out of the deal goes against advice from several aides of his, including his daughter Ivanka Trump and chief strategist Steve Bannon.

Trump's son-in-law and top aide, Jared Kushner, was said to be neutral on the deal, and concerned about the legal ramifications of reducing USA carbon reduction commitments below what Obama pledged.

Trump promised during his presidential campaign to pull the US out of the deal.

Axiosreported that the manner of the withdrawal was still being hashed out by Trump's advisors, which might explain the delay of a formal announcement.

Trump, who has previously called global warming a hoax, came under concerted pressure from the other leaders to honour the agreement on curbing carbon emissions.

There have been influential voices urging Trump not to ditch the Paris accord.

If Trump pulls out of the accord, the US would become largest greenhouse gas emitter not included in the 2015 pact agreed upon by almost 200 countries to curb climate-changing carbon emissions.

But Republicans have slammed the climate deal and Trump joined the chorus when he ran for president.

Speaking in May, British member of the European Parliament Janice Atkinson attacked the Paris deal as creating stealth taxes, and praised President Trump for potentially taking the United States out of the agreement, as it would encourage others.

And Sweden's Climate Minister Isabella Lovin says "it would be deeply regrettable" if the United States decides to pull out of a landmark global climate agreement, adding "it is also contrary to what we expect from the USA leadership when humanity faces major challenges". And leaders from coal-producing states have pressed Trump to uphold his vows to cancel USA commitments to Paris.

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